Fuel in a fuel tank is sent to an internal combustion engine through a suction pipe and so on disposed in this fuel tank. A filter apparatus is attached to a fuel suction opening of such a suction pipe in order to remove water from the fuel thus sent and to prevent dust from being sent into a fuel pump. As such a filter apparatus, there is one shown in Patent Document 1 disclosed by the present applicant.
Inside the filter apparatus of Patent Document 1, there is a bag-like filter body having an internal space which is connected to the fuel suction opening inside the fuel tank. Such filter body has three layers of filter materials made of an unwoven cloth produced by melt-blown method between the outermost filter material made of a woven fabric mesh and the innermost filter material made of an unwoven cloth produced by spun-bond method. Also, it is made such that an average aperture diameter of the unwoven cloth produced by melt-blown method positioned on the inside becomes smaller than an average aperture diameter of the unwoven cloth produced by the melt-blown method positioned on the outside, whereby a filtration gradient is given to the filter body. In this way, while it is made such that fine dust can be captured, the burden on the filter material made of the unwoven cloth produced by the melt-blown method positioned on the inside having a small average aperture diameter is reduced so as to achieve a long life of the filter apparatus. Also, generally, a secondary filter for capturing additional fine dust is provided on the downstream side of the fuel pump. However, in the case that the filter apparatus of Patent Document 1 is used, such secondary filter can be eliminated.
Here, generally, it is said that dust mixed inside the fuel tank corresponds to JIS test powder 1 (JIS Z 8901) including seven kinds. (Hereinafter, called JIS 7) In this JIS 7 powder, approximately 90% of a total thereof is constituted by particles having a particle diameter of 30 μm or less. (See Table 1/the number of particles in 10 milliliters of 200 milliliters of a test liquid wherein 60 mg of the JIS 7 powders are mixed, was measured.)
TABLE 1Particle Diameter:Number of ParticlesUnit μmCumulative NumberRelative Ratio 5 or more251794100.0%10 or more18786874.6%20 or more8278832.9%30 or more3206112.7%40 or more134035.3%50 or more52982.1%70 or more3300.1%100 or more 40.0%(Measured by a particle counter)
Patent Document 1: Japanese Unexamined Patent Application